Stringent performance requirements can magnify the impact to performance degradation induced by Design-for-Testability (DfT) techniques. Controllability and observability of each flip-flop has typically been ensured via an insertion of a scan multiplexer yet at the expense of functional path prolongation by a multiplexer delay. While such a transformation on every flip-flop can eliminate the sequentiality of the test generation problem, critical path prolongation and thus functional speed degradation can be the end-result, undermining the expected fulfillment of the stringent performance requirements. As more aggressive performance optimizations are being employed, resulting in high-performance designs with reduced logic depth, the impact of scan multiplexers can be even more magnified.
Traditionally, partial scan has been an approach for eliminating/alleviating the performance penalty of scan. Research has been conducted in partial scan designs, typically targeting the removal of scan multiplexers on a set of selected flip-flops. The consequent benefit can be potential alleviation of the performance penalty of scan, in addition to other benefits such as test time, e.g., data volume and power reduction. The previously described techniques in partial scan can be classified mainly into three categories, e.g.: structure-based techniques that typically involve breaking the cycles and/or reducing scan depth, testability-based techniques that can select scan flip-flops based on testability improvements, and test generation-based techniques which can intertwine test generation and scan flip-flop selection. Other partial scan techniques can include those driven by layout constraints, timing constraints, re-timing, and toggling rate of flip-flops and entropy measures. These traditional techniques typically necessitate the utilization of sequential ATPG (or combinational ATPG with time frame expansion), however, to generate test patterns on a partially scanned design, which can not only fail to comply with the existing design/test flow that industry utilizes, but also can be incapable of ensuring the quality of full scan.
Accordingly, there can be a need to address and/or overcome at least some of the above described deficiencies and issues.